Ethanol in Fuel: Ruining Fuel Systems in Boats


Normally, boat owners would prefer getting gas without ethanol as it is poses potential dangers for boat and marine engines. However, the sad reality is that finding ethanol-free gas today is close to impossible. This is particularly because not all states require gas-pumps to specify the presence of ethanol in their fuels. Therefore, it is highly probable your boat is currently using E10 and you are not even aware of it.

Did you know alcohol has been a fuel additive for the past 100 years? Several outboard motors built in the 1990s or later were specifically designed to run on ethanol fuel. But the fact of the matter is those times no longer exist and the engines manufactured today are a lot more advanced. Many studies indicate alcohol is harmful to gas fuel systems and their engines, and this has proven particularly true for the boat market.

Here’s a detailed look at ethanol in fuel and how it can ruin the fuel systems in boats:

What Are Ethanol and Ethanol-Blended Fuels?

Basically, ethanol is used for its oxygenating properties. Hence, it is added to fuels to decrease hydrocarbon emissions that lead to air pollution. It can be made from natural products, such as wheat, corn and sugar cane. However, modern technology now permits ethanol to be produced from cellulosic feedstock, including corn stalks, municipal waste, wood chips, pulp, paper and other sources.

Ethanol-blended fuels, also referred to as E10, are fuels which contain 90% gasoline and 10% ethanol. Similarly, E15 fuels contain 85% gasoline and 15% ethanol. That’s not all though. There are a number of other varieties available as well, which include, E20, E25, E70, E75, E85, ED95 and E100.  

How Is Ethanol Produced?

In the US, ethanol is generally made by removing the sugar and starch portion of corn. The starch is fermented and then distilled into alcohol. After these processes, any excess water found is removed, which results in extremely pure, ethyl alcohol, better known as ethanol. In other countries, ethanol is produced from a variety of raw materials. For example, wheat straw and sugar beets are used to produce ethanol in Europe, while sugar cane is commonly used in Brazil.

The Problems Associated With Ethanol Fuels

Now that you aware of what ethanol and ethanol-blended fuels are and how they are commonly produced, let’s move on and discuss the various problems they can cause for your boat’s fuel system:

Engine Damage or Failure

Ethanol is a powerful solvent. Hence, it will clean out gunk particles that build up in the engine and fuel lines as you use it. However, if you put ethanol into an already dirty fuel system (which is the case with most old motors), it will dislodge carbon residues. These may work their way into the engine and damage internal parts or block fuel flow. Old rubber gaskets may also wear out quickly, resulting in engine failure.

Moisture Absorption

Unlike vehicles, fuel tanks in boats and marinas are vented. So, the fuel will be partly exposed to the air. As your boat will be near water (why wouldn’t it be anyways?) the ethanol content could attract moisture. This can be tricky, especially if your fuel line does not have a water/fuel separating filter, as the water can get into the motor.

Moisture absorption can lead to another major problem as well. Once enough moisture has been absorbed into the fuel, it can result in phase separation, which causes a layer of gas to float over the ethanol and water in your fuel tank. If this happens with you, pull over immediately as the engine could be drawing nothing but water and alcohol!

Microbial Growth

As if the abovementioned problem wasn’t enough, the presence of water in fuel can also lead to microbial growth. Yes, you read that right. Apart from rusting and corrosion occurring in the engine, there is the risk of mold, fungi, and other bacteria building up. As expected, this can cause a number of unwanted problems inside the engine.

Stale Fuel

As surprising as this may sound, it isn’t a new phenomenon. Fuel can get stale over time, much the same way soda gets flat. How? That’s because ethanol can cause the fuel to become stale quicker than if it were completely pure. Stale fuel can lead to many problems inside the boat’s engine. Moreover, as boats are used less often than vehicles, the stale fuel is more likely to come into effect.

Other Problems

That’s not all. There are a number of other problems that can be caused by using ethanol and ethanol-blended fuels in your boat, which can include the following:

Fuel leaks and fuel system clogs.

Sputtering, stalling motor.

Rusting and deterioration of parts.

Difficulties in maintain speed.

Engine fails to accelerate when pressing on the throttle.

How to Prevent these Problems?

As you can see, ethanol in fuel can lead to several problems in the boat’s fuel system and engine. However, the good news is most of these problems can be avoided with ease. All you have to do is follow a few simple measures:

Take Care of Problems Immediately

If you are facing repetitive performance issues, such as a fouled carburetor, a proactive approach should fix the problem. One good way is to pump the tank dry and replace it with fresh gas. If possible, try to get ethanol-free gas. It is the best solution. However, as mentioned earlier, it’s close to impossible to find 100% gasoline. If you own a boat and have tried finding it, you will know what we are talking about here!

Check for the Presence of Water

Inspect your fuel tank or water/fuel separating filter for the presence of water. If you do find water, you should either siphon the tank dry or pump the tank dry from the fuel line. Then, pour the fuel into a clear container and examine it thoroughly. If the fuel has a sour odor or is unclear, it’s recommended you get your tank cleaned up.

Avoid Using Ethanol Gas that is Old

You should always avoid using ethanol gas that is more than 90 days old. This is particularly true if you are using your boat after a long period of time. As ethanol can cause the gas to become stale faster than usual, the gas is likely to absorb water and cause various other problems. In such cases, replacing the gas should do the trick.

Perform Routine Maintenance

Whether you are facing problems or not, keeping up with your maintenance schedule is extremely important! Hence, it is recommended you perform routine maintenance tasks, such as keeping your carburetor clean and changing fuel filters, as it can go a long way in reducing the build-up of sludge in your engine caused by ethanol.

Purchase Gas that Will Last You 30 Days

Ethanol speeds up the deterioration process of fuels, which can prevent the engine from running or cause it to perform poorly. Worst case scenario, the gummy deposits that form due to the continual deterioration of fuel can cause fuel leakages from the carburetor. Due to these reasons (and many more!), it’s a great idea to only purchase the amount of gas that will be last you 30 days, rather than fueling your boat up and leaving some to deteriorate over time.

Never Use Fuels that Contain More than 10% Ethanol

Let’s face it, with E10 having the potential to cause numerous problems, we can only imagine the issues fuels containing more than 10% ethanol can cause! However, it’s obvious you cannot determine the type of fuel just by looking at it. You will have to send a sample of the fuel to a laboratory, so they can perform relevant tests. Although this can cost you some money, the findings of these tests can help you identify fuels containing more than 10% ethanol before you actually use them!

Use Quality Fuel Treatment

There are several additives available in the market, which can counteract some of the effects of ethanol gas. However, when you are out shopping for them, make sure you read their labels carefully. That’s because most additives contain ethanol or other alcohol-related products. And it goes without saying that adding more alcohol cannot fix a problem caused by alcohol in the first place.

A quality fuel treatment combines alcohol-free ethanol protection, detergents and combustion improvement in a single product. And that’s exactly what you should be looking for. The best additives contain alcohol-free water absorbing ingredients, which improve engine performance, cut engine emissions and enhance fuel efficiency lost due to ethanol.

Final Words

There you have it! By understanding the various problems ethanol can cause to your boat’s fueling system, and the ways you can prevent them from happening, you can ensure your boat runs well, even if it’s fueled with gas that contains ethanol!

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